a) Field of the Invention
This invention relates to a process for subjecting oil or fat to a hydrolytic reaction in a layer packed with an immobilized enzyme, which features allowing the immobilized enzyme to more effectively exhibit its activity so that the productivity is increased while making an improvement in the serviceability of the immobilized enzyme.
b) Description of the Related Art
Hydrolytic processes of oil and fat, which make use of immobilized enzymes, include continuous processes, which use reactors such as packed-column (fixed-bed) reactors, fluidized-bed reactors and falling-film reactors, in addition to non-continuous processes using agitated reactors. With conventional techniques, however, such immobilized enzymes are low in hydrolytic activity and moreover, their hydrolytic activity is lowered further due to separation or the like of the enzymes.
JP-A-61085195A discloses a process which comprises countercurrently feeding water and oil or fat as liquid reactants from the top and bottom of a vertical packed column, respectively, to bring them into contact with each other. The liquid reactants are brought as continuous phases into contact with an immobilized enzyme. To avoid emulsification of water and the oil or fat, their feeding rates are 7.6×10−3 mm/min, i.e., are extremely low, and the residence time required for the reaction ranges from several tens to several hundreds of hours, that is, is long. This process also involves additional problems that special facilities and operation method are required to countercurrently feed the two liquids to the packed column.
On the other hand, a system in which water and oil or fat are concurrently fed in the same direction to bring them into contact with each other is also accompanied by a problem that the residence time is long.
Processes, each of which makes use of a fluidized bed reactor [for example, J. Am. Oil Chem. Soc., 72, 1281 (1995)], require residence time as long as 40 hours, and have not succeeded yet in achieving any high hydrolysis yield in short time.
Processes, each of which makes use of a membrane reactor [for example, J. Am. Oil Chem. Soc., 62, 1016 (1985)], are low in the permeability of a liquid reaction mixture through enzyme-immobilized membranes, resulting in very low hydrolytic reaction rates.
Further, no publication is known to disclose a method for controlling a reduction in the activity of an immobilized enzyme, specifically a method for improving its serviceability.
In the conventional processes each of which hydrolyzes oil or fat by feeding it to an immobilized enzyme and bringing it into contact with the immobilized enzyme, any attempt to increase the efficiency of the reaction by the enzyme requires prolonging the time of contact between the enzyme and the oil or fat to increase the residence time of the liquid reactant(s) as described above. In addition, the activity of each immobilized enzyme is lowered in short time so that its serviceability is poor. Frequent replacement of the immobilized enzyme is, therefore, needed to retain high productivity.